Oil wells and many other types of wells often comprise a wellbore lined with a steel casing. A casing is a string of pipes that are threaded at each end to be interconnected by a series of internally threaded pipe couplings. A lower end of the casing is perforated to allow oil, water, gas, or other targeted fluid to enter the interior of the casing.
Disposed within the casing is another string of pipes interconnected by a series of threaded pipe couplings. This internal string of pipes, known as tubing, has a much smaller diameter than casing. Fluid in the ground passes through the perforations of the casing to enter an annulus between the inner wall of the casing and the outer wall of the tubing. From there, the fluid forces itself through openings in the tubing and then up through the tubing to ground level, provided the fluid is under sufficient pressure.
If the natural fluid pressure is insufficient, a reciprocating piston pump is installed at the bottom of the tubing to force the fluid up the tubing. A reciprocating drive at ground level is coupled to operate the pump's piston by way of a long string of sucker rods (or “rods”) that is driven up and down within the interior of the tubing. A string of sucker rods is typically comprised of individual solid rods that are threaded at each end so they can be interconnected by threaded couplings.
Since casings, tubing and sucker rods often extend thousands of feet, so as to extend the full depth of the well, it is imperative that their respective coupling connections be properly tightened to avoid costly repair and downtime. Couplings for tubing (i.e., couplings for tubing and casings), and couplings for sucker rods are usually tightened using a tool known as tongs. Tongs vary in design to suit particular purposes, i.e., tightening tubing or rods, however, each variety of tongs shares a common purpose of torquing one threaded element relative to another. Tongs typically include a hydraulic motor that delivers a torque to a set of jaws that grip the element or elements being tightened.
As a function of preventative maintenance or when maintenance is to be done on portions of the well, the sucker rods and tubing can be removed from the well to conduct an analysis of or fix wellbore conditions. As the sucker rods and tubing are removed from the well, each rod and/or tubing must be broken out from the coupling that attaches one rod to another. Once a breakout of the rod or tubing has occurred, the operator must determine if the rod or tubing will be reused or if it is too badly damaged. If the sucker rods and/or tubing are of poor quality, such as having damaged threads, they can leak and cause further damage to it and other components in the well. How the sucker rods and tubing break out can also be a predictor of future pin failures in the rods or tubing. If the breakout occurs at pressures substantially above those that are expected, the cause may be linked to damaged threads, which will limit the ability for that rod to create a proper seal if it is made-up and run back into the well. On the other hand, if the breakout occurs at pressures substantially below those that are expected, the cause may be linked to the pump or to a rod/pump interaction.
Various quality control procedures have been developed in an attempt to ensure that only sucker rods and tubing of good quality are reused in the well. However, operators and rig personnel are often under a tight timeframe to remove the sucker rods and tubing, fix the well, and rerun the equipment back into the well. In many cases, operators are too busy to give proper attention to rods and tubing that may already be damaged. Consequently, a need exists for a display system and evaluation methodology that records and evaluates the breakout pressures for sucker rods and tubing and notifies the operator of the rig if the breakout pressures are outside of an expected range, thereby identifying those rods and tubing most likely to need replacement.
The present invention is directed to solving these as well as other similar issues in related to the breakout of rods and tubing.